DataStax Support Forums » Topic: Replication in two data center configurationhttp://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration
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Anonymous on "Replication in two data center configuration"http://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration#post-1453
Wed, 28 Mar 2012 17:39:05 +0000Anonymous1453@http://www.datastax.com/support-forums/<p>Appreciate the responses. We'll probably end up going with a 2 and 2 setup after we get a few more nodes up, thanks!!
</p>jbellis on "Replication in two data center configuration"http://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration#post-1364
Tue, 13 Mar 2012 16:38:00 +0000jbellis1364@http://www.datastax.com/support-forums/<p>"Two copies local, one copy remote" is not supported, because then the replicas would have to change depending on which DC you're querying from.</p>
<p>OldNetworkTopologyStrategy would allow 3 total replicas, where sometimes the 3rd is in DC1, and other times in DC2 (deterministically). Or you could just leave it as just two replicas, or four as Jackson suggested.
</p>jackson@datastax.com on "Replication in two data center configuration"http://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration#post-1363
Tue, 13 Mar 2012 16:14:07 +0000jackson@datastax.com1363@http://www.datastax.com/support-forums/<p>Hello Alvin,</p>
<p>When setting up strategy option as "{DC1:2,DC2:1}", Cassandra will place 2 replicas in DC1 and 1 replica in DC2, as you have observed. This is the expected behavior.</p>
<p>All replicas are the same in Cassandra. There is no concept of replicating an extra copy within the "local datacenter", and replicate once in the "remote". You could do "{DC1:2, DC2:2}" such that each datacenter has 2 replicas for every write it receives.</p>
<p>Regards,<br />
Jackson
</p>Anonymous on "Replication in two data center configuration"http://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration#post-1361
Tue, 13 Mar 2012 11:39:54 +0000Anonymous1361@http://www.datastax.com/support-forums/<p>Any ideas?
</p>Anonymous on "Replication in two data center configuration"http://www.datastax.com/support-forums/topic/replication-in-two-data-center-configuration#post-1333
Wed, 07 Mar 2012 14:38:09 +0000Anonymous1333@http://www.datastax.com/support-forums/<p>Hi all, thanks in advance for your help! :)</p>
<p>Our team has a two data center configuration. We have a 6 node cluster with 3 nodes on each site. We want to have a replication factor of 3, replicating once to the local site and once cross site. Currently, we are using strategy_options={DC1:2,DC2:1}; for our keyspace, but notice that DC1 will always have two replicas while DC2 will always only have one replica, regardless of node.</p>
<p>What is the suggested way to specify our strategy so that each node will replicate once locally and once cross site?</p>
<p>Thank you!!<br />
Alvin
</p>